Williams' fifth victory in five career matches with Pennetta sets up a quarterfinal clash with either Sloane Stephens or Jelena Jankovic on Friday.

"I got an early break and just didn't let go," Williams said, according to wtatennis.com. "That's what I wanted to do because she has the ability to come back. Even in the end she tried to make a comeback, but I just stayed focused."

Williams struck eight aces on the day, and tallied 28 winners against 25 unforced errors against Pennetta. Williams raced out to a 3-0 lead in the opener, and finally closed the set after an eight-deuce game when a Pennetta backhand found the net.

Williams would race out to a 5-0 lead in set two before Pennetta claimed the next two games, but the Italian’s rally was thwarted in the next game as Williams broke serve for the fifth time on the day when her backhand return clipped the tape and dropped in for a let cord winner, closing the affair in just over an hour.

Halep Advances Past Safarova>>>

Second seed Simona Halep eased past Lucie Safarova in straight sets earlier on Thursday, 6-4, 7-5. The Romanian won her third straight against Safarova, and will move on to face either Maria Sharapova or Anastasia Pavlyuchenkova in the quarterfinals on Friday.

Though Halep was broken twice on the day, she only dropped ten points on serve during the 88-minute match.